B&N follow-up (updated)

Following up on this, a kind friend allowed me to use her US credit card in the B&N ebook store. But check this: I filled out all data, and successfully bought an issue of WSJ for a buck to test it, and it all went fine, until the moment I tried to download it. Then I was told there was "an issue" with the payment.
Then a bit later I got an email from them which said that I had to be physically present in the US to buy their ebooks!

What the heck kind of law or rule requires such draconian measures?
(Like my friend says: "What if I were traveling overseas and wanted a book to read?")

And how come Amazon has no trouble selling me books, electronic or otherwise? Even with a UK or Danish credit card. (I bought my first Kindle ebook on October 21, 2009, well before they had a UK Kindle store.)

Update: 
B&N tells me in an email:
We must comply with copyright rules governing the sale and use of digital content. These rules currently require that all eBook purchases from our website be made within the United States and U.S. Territories (or Canada). Although we are investigating options that will help safeguard author and publisher rights while making eBooks available for purchase outside the above-named areas, only customers physically located in the U.S. and Canada are able to purchase eBooks on the Barnes & Noble website at this time.
Please accept our sincere apologies for any inconvenience this may cause.

OK then.
I wonder why it would be different for Amazon though. Maybe they bar books on an individual basis, and B&N doesn't have the resources for that yet?

Further, I have never heard of a book store refusing to sell a book to a customer in another country before. Amazon surely never has, I have bought hundreds of books, CDs, and DVDs from their US store since the nineties.